A cold smoker is used for food that needs to be smoked for an extended period of time, but doesn't require the cooking process of a barbecue. To build such a cold smoker, you need a 55-gallon drum, an electric drill and a saw, several coils of metal grill or stove grate, and metal ductwork or metal pipe. The 55-gallon drum needs to be cut in half side to side, and the top and bottom portions of the drum need to be sealed with the metal grill or stove grate. The metal pipe or ductwork needs to be sized to fit snugly in the center of the drum, and it should be long enough to extend over the top of the drum. When the pipe or ductwork is in place, it needs to be curved downward so that food can fit on top of it. The pipe or ductwork needs to be sealed with metal duct sealer. Duct sealer can be found at most hardware stores.